The usefulness of rigid foamed polymeric boards in a variety of applications is well known. Rigid foamed plastic boards are extensively used as thermal insulating materials for many applications. For instance, polymeric foam boards are widely used as insulating members in building construction. In the past, infrared attenuating agents have been used as fillers in polymeric foam boards to minimize material thermal conductivity k which, in turn, will maximize insulating capability (increase R-value) for a given thickness (U.S. Pat. Nos. 5,373,026 and 5,604,265; EP 863,175). The heat transfer k through an insulating material can occur through solid conductivity, gas conductivity, radiation, and convection. The heat transfer k, or K-factor, is defined as the ratio of the heat flow per unit cross-sectional to the temperature drop per unit thickness. In U.S. units, this is defined as:
      Btu    ·    in              Hr      ·              Ft        2            ·      °        ⁢                  ⁢          F      .      
And the metric unit:
  W  mk
In most polymeric foams of conventional cell size, i.e. 0.1 to 1.5 millimeters, the reduction of thermal conductivity k has been observed with decreasing the average cell size. This phenomenon is documented in “The Thermal Conductivity of Foamed Plastics,” Chemical Engineering Progress, Vol. 57, No. 10, pp. 55-59, authored by Richard E. Skochdopol of The Dow Chemical Co., and “Prediction of the Radiation Term in the Thermal Conductivity of Crosslinked Closed Cell Polyolefin Foams,” J. of Polymer Science: Part B: Polymer Physics, V 38, pp. 993-1004 (2000), by O. A. Almanza et al. of Universidad de Valladolid, which are herein incorporated by reference.
It is highly desirable to improve the thermal conductivity k without adding additives, or increasing the density and/or the thickness of foam product. Particularly, the architectural community desires a foam board having a thermal resistance value R equal to 10, with a thickness of less than 1-¾ inches, for cavity wall construction, to keep at least 1 inches of the cavity air gap clean. The total thermal resistance R, also known as the R-value, is the ratio of thickness t of the board to thermal conductivity k.
It is also highly desirable to produce the above rigid polymer foam having retained or improved compressive strength, thermal dimensional stability, fire resistance, and water absorption properties.
It is also highly desirable to provide the above rigid polymer foam with infrared attenuating agents and other process additives, such as nucleating agent, fire retardant, gas barrier, which has overall compound effects on foam properties including improved thermal conductivity (decreased k-factor), and improved insulating value (increased R-value) for a given thickness and density.
It is also highly desirable to provide the above rigid polymer foam with variety of blowing agents to enhance the thermal insulation R-value. These blowing agents include partially or fully hydrogenated chloroflourocarbons (HCFC's), hydroflourocarbons (HFC's), hydrocarbons (HC's), water, carbon dioxide, and other inert gases.
It is also highly desirable to provide the process methods and foaming facility modification to control the cell morphology: reduce the cell anisotropic and increase cell orientation during foaming process, for use in the production of a rigid polymer foam.
It is also highly desirable to lower the cost of a polymeric foam product in a simple and economical manner.